memory controller: soft limit interface
Add an interface to allow get/set of soft limits. Soft limits for memory
plus swap controller (memsw) is currently not supported. Resource
counters have been enhanced to support soft limits and new type
RES_SOFT_LIMIT has been added. Unlike hard limits, soft limits can be
directly set and do not need any reclaim or checks before setting them to
a newer value.
Kamezawa-San raised a question as to whether soft limit should belong to
res_counter. Since all resources understand the basic concepts of hard
and soft limits, it is justified to add soft limits here. Soft limits are
a generic resource usage feature, even file system quotas support soft
limits.
Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/res_counter.h b/include/linux/res_counter.h
index 511f42f..fcb9884 100644
--- a/include/linux/res_counter.h
+++ b/include/linux/res_counter.h
@@ -35,6 +35,10 @@
*/
unsigned long long limit;
/*
+ * the limit that usage can be exceed
+ */
+ unsigned long long soft_limit;
+ /*
* the number of unsuccessful attempts to consume the resource
*/
unsigned long long failcnt;
@@ -87,6 +91,7 @@
RES_MAX_USAGE,
RES_LIMIT,
RES_FAILCNT,
+ RES_SOFT_LIMIT,
};
/*
@@ -132,6 +137,36 @@
return false;
}
+static inline bool res_counter_soft_limit_check_locked(struct res_counter *cnt)
+{
+ if (cnt->usage < cnt->soft_limit)
+ return true;
+
+ return false;
+}
+
+/**
+ * Get the difference between the usage and the soft limit
+ * @cnt: The counter
+ *
+ * Returns 0 if usage is less than or equal to soft limit
+ * The difference between usage and soft limit, otherwise.
+ */
+static inline unsigned long long
+res_counter_soft_limit_excess(struct res_counter *cnt)
+{
+ unsigned long long excess;
+ unsigned long flags;
+
+ spin_lock_irqsave(&cnt->lock, flags);
+ if (cnt->usage <= cnt->soft_limit)
+ excess = 0;
+ else
+ excess = cnt->usage - cnt->soft_limit;
+ spin_unlock_irqrestore(&cnt->lock, flags);
+ return excess;
+}
+
/*
* Helper function to detect if the cgroup is within it's limit or
* not. It's currently called from cgroup_rss_prepare()
@@ -147,6 +182,17 @@
return ret;
}
+static inline bool res_counter_check_under_soft_limit(struct res_counter *cnt)
+{
+ bool ret;
+ unsigned long flags;
+
+ spin_lock_irqsave(&cnt->lock, flags);
+ ret = res_counter_soft_limit_check_locked(cnt);
+ spin_unlock_irqrestore(&cnt->lock, flags);
+ return ret;
+}
+
static inline void res_counter_reset_max(struct res_counter *cnt)
{
unsigned long flags;
@@ -180,4 +226,16 @@
return ret;
}
+static inline int
+res_counter_set_soft_limit(struct res_counter *cnt,
+ unsigned long long soft_limit)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&cnt->lock, flags);
+ cnt->soft_limit = soft_limit;
+ spin_unlock_irqrestore(&cnt->lock, flags);
+ return 0;
+}
+
#endif